Correctly quote date-like strings

[autrilla]

Fixes #192

(this is a copy of #193, but since then, we've needed to move the fix to another branch)

[autrilla]

I'm not sure why this is broken on tip

[vinzenz]

@autrilla It's fixed by #217 - It's a change in the time stdlib

[rogpeppe]

Fixed by #310.

[autrilla]

@rogpeppe I'm not sure this is fixed, unless I'm misunderstanding things. Running the reproduction case from the issue:

cd /tmp && mkdir gotmp && export GOPATH=/tmp/gotmp && go get -u gopkg.in/yaml.v2 && cat <<EOF > main.go && go run main.go
package main

import (
    "fmt"
    "gopkg.in/yaml.v2"
)

func main() {
    m := make(map[string]string)
    m["foo"] = "2006-01-02T15:04:05Z"
    out, _ := yaml.Marshal(m)
    fmt.Println(string(out))
}
EOF

Outputs:

foo: 2006-01-02T15:04:05Z

But if it was fixed, it should have output the date string quoted with single or double quotes.

Edit: Oh, never mind, I see this is on the devel branch.